Can end seal



March 21, 1967 w. L. FLAHERTY CAN END SEAL 2 sheets sneet 1 Filed July 15, 1964 f1 Mum FM.

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I N VE NTOR. WALTER L FLAHERTY BY w S Q a AGENT March 21, 1967 w. FLAHERTY CAN END SEAL Filed July 15, 1964 2 Sheets-Sheet 2 FIG.4

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WALTER L. FLAHERTY BY w -Q xxmm AGENT United States Patent 6 Connecticut Filed July 15, 1964, Ser. No. 382,812 4 Claims. (Cl. 220-67) This invention relates to containers and, in particular, to cans having an improved seal at that portion where the can lid overlaps the side seam of the container body and to a method for making the improved seal.

In conventional can manufacture, the opposed side seam edges of a sheet metal can body blank are r'eversely bent to form body hooks which are interengaged and bumped together to form a side seam. In order to provide a hermetic seal, solder is applied to the exterior of the locked seam or a cement may be used which is applied to at least one of the body hooks before the hooks are interengaged and locked together. After the side seam is completed, the opposed open ends of the resulting tubular can body are outwardly flanged at their marginal edges for sealing engagement with the can lids.

The can lids are made in a separate operation by stamping a blank from like material which may be tin plate, black plate, aluminum or other sheet metal. In general, the blank is stamped into the desired configuration, e.g., circular, oval or rectangular and is formed with a countersunk panel which merges into a substantially vertical surrounding wall section. The outer edges of the wall section merge into a substantially horizontal annular flange which terminates in an inwardly curled edge. A fiowable sealing composition is applied to the under surface of the annular horizontal flange within the annular channel defined by the vertical wall section and edge curl. The com pound is usually deposited in the channel using conventional nozzle lining machinery but may be applied in any other suitable and convenient manner. After the can lids have been lined, they are conveyed to a drier where the volatile components of the sealing composition are removed. Thereafter, a lined can lid is double seamed to a can body and the open end can is shipped to the packer who, after filling the can, double seams the top lid in place.

This method generally provides sealed containers which are air tight. However, leaks occasionally occur at the point where the can lid engages the lap area of the can body where several layers of metal forming the locked seam are interfolded with the end closure. Such leaks can occur at one or both ends of the can and obviously, a leak at either one may lead to spoilage of the can contents. Attempts have been made to eliminate any possibility of leakage by placing additional sealing compound in that portion of the can lid channel which ultimately would overlap the side seam of the can body. Such attempts have not been altogether satisfactory because there is no rapid means of accurately registering that portion of the can lid which carries the additional sealing compound with the lap area of the can body during the double seaming operation.

It is, therefore, an object of this invention to provide containers, such as tin cans, with assured hermetic seals and a rapid means for fabricating the same. This objective is achieved by providing can body blanks having a strip of sealing composition disposed lengthwise along each of the opposed marginal edges which ultimately are flanged and interfolded with the end closures wherein the thickness of each strip is greater at each of its opposed longitudinal end portions. After the side seam edges are shaped and interlocked in a known manner, the strips of sealing composition become positioned at either end of the tubular body as circumferential bands of material on the inner surface of the edges defining the open ends which subsequently are outwardly flanged for sealing engagement with the top and bottom end closures. The extra film volume of compound disposed at the opposed end portions of each longitudinal strip of sealing composition become located in the lap area of the side seam. By first applying the sealing composition to flat stock of can body blank material, the additional amount of composition has a fixed place in the finished can body and therefore, no additional care is required to assure registration of the side seam with the can lid during the double seaming operation.

A particularly effective and rapid method for applying the sealing composition to the can body blank comprises depositing a liquid sealing composition on a length or sheet of flat stock in a repeated pattern of spaced linear configurations of predetermined length, drying the sodisposed composition, and thereafter cutting the flat stock into individual can body blanks having a strip of composition disposed lengthwise on each of its marginal edges which are subsequently engaged with a can lid by double seaming.

One embodiment of this method involves the use of a cylindrical printing surface having the linear design incised therein in intaglio. The design is made up of a multiplicity of linearly-arranged small, independent, noncommunicating recesses formed by drilling, engraving, etching or other method. The printing cylinder rot-ates over a bath of liquid sealing composition where the composition is received into the depressions in the cylinder surface. Upon further rotation, these depressions meet with the sheet stock and the sealing composition is transferred thereto. The transfer of the printed composition of each pattern is initially in the form of small individual dots which may coalesce immediately or may be caused to flow together by heating to form individual but continuous strips. The composition printed on the sheet is then set to a form-stable condition by any convenient method, such as heat, and the heat-treated sheet is passed to a stack of similar sheets for subsequent cutting and can formation.

The location of extra sealing material at the lap area of the finished can is achieved by varying the depth of the depressions on the printing cylinder surface. These depressions have a uniform depth and diameter through the central region of the pattern with deeper recesses and if desired, depressions of slightly larger diameter being provided at each of the longitudinal extremities. Thus, when the printing cylinder rotates over the bath containing the sealing composition, a greater amount of composition is received by the extremities of the pattern which results in a deposit of a thicker layer at these portions when the pattern is transferred to the sheet stock. When the printed sheets are cut into individual can body blanks and side seamed, the extra sealing composition resides in the lap area at each end of the can body for perfect registration with any portion of the can lid during the double seaming step. Consequently, additional composition is always assured in the lap area of the double seam irrespective of the method employed in aflixing the can lids to the can body.

The invention is further illustrated by reference to the attached drawings which describe one method of applying the sealing composition to blanks.

FIGURE 1 schematically illustrates a printing process used to produce can body sheet stock having strips of sealing composition applied thereto.

FIGURE 2 is a perspective view of a printing cylinder having a design in intaglio for printing the strips of sealing composition onto the sheet stock.

FIGURE 3 shows a portion of the can body sheet stock bearing the printed strips of sealing composition.

FIGURE 4 is a plan view of an individual can body blank cut along the interrupted lines from the sheet stock of FIGURE 3 having strips of sealing composition disposed lengthwise along a pair of the opposed marginal edges.

FIGURE 5 is a side view of the body blank of FIG- URE 4.

FIGURE 6 is a perspective view of the body blank of FIGURES 4 and 5 after shaping but prior to interengaging and interlocking the body hooks to form the side seam.

FIGURE 7 is a fragmentary sectional view of the lap area of one end of the body formed from the shaped blank of FIGURE 6 showing a can lid in position incident to double seaming and showing the thickened end portions of a strip of sealing composition in the lap area of the side seam.

Referring to FIGURE 1, a sheet 2, such as tin plate, and adapted to receive the strips of sealing composition is delivered from a feeder 3 containing a supply of blank sheets to a first conveyor 4. The conveyor moves the sheet to the printing site where pressure roll 5 is superimposed over rotating printing cylinder 6. The surface of cylinder 6 is provided with a repeating pattern 7 of linear configuration (shown in FIGURE 2) incised in intaglio. As the cylinder rotates, its sunface is immersed in a bath 8 of sealing composition 17, disposed beneath cylinder 6, and is received in the incised areas defining pattern 7. Suitable compositions are illustrated in Examples 1-4. Means, such as doctor blade 9, are provided to remove the composition which adheres to the cylinder surface.

Sheet 2 is then passed into the nip between roll 5 and cylinder 6 where the composition in the pattern is transferred onto the underside of the sheet. Movement and spacing of sheets on the conveyor 4 and the rotation of cylinder 6 are synchronized to effect a coincidental meet ing of the sheet and the pattern 7. The printed sheet is then passed to the underside of a second conveyor belt 10 with the sheet being held magnetically in this position. Suitable attractive forces for holding the sheet on the underside of the belt may be developed by imbedding magnetic particles in the outer surface of the belting. If an aluminum sheet is used, the magnetic force may be eliminated and such sheets may be held in place by vacuum instead.

The movement of conveyor belt 10 is guided upwardly by means of roll 11 and returned to a horizontal position as it passes over roll 12 which upturns the sheet 2. On its return passage to the cylinder 6, the belt 10 is directed downwardly by roll 13 and passed over roll 14 where it again :follows a horizontal path. The upturned sheet 2 then passes through a drying zone 15 where the volatile constituents of the composition are expelled, and then the sheet is transferred to a third conveyor belt 16 which carries it to a series of working stations (not shown) where individual body blanks are cut and thereafter formed into can bodies.

In FIGURE 2 the printing cylinder 6 is shown having a linear design 7 incised in its printing surface in intaglio. The design is made up of a multiplicity of linearlyarranged small, independent, non-communicating recesses of uniform depth throughout the central portion of each pattern but of greater depth at each of the longitudinal extremities. The recesses receive the sealing composition as the cylinder rotates over the bath. Thereafter, the composition is transferred from the recesses to the sheet stock as a multiplicity of spaced dots.

In FIGURE 3 a portion of sheet 2 is shown after the sealing composition 17 has been applied on its surface and after the dots of composition have coalesced into a linear pattern. The sheet 2 is then moved to a drier and subsequently cut along the interrupted lines to form individual can body blanks.

FIGURE 4 shows an individual can body blank 20 cut ell) from the sheet of FIGURE 3. The blank includes opposed side seam edges 21 and 23 and opposed marginal edges 22 and 24, the latter of which are ultimately interfolded with a can lid to form a double seam. Disposed lengthwise along the marginal edges 22 and 24 are coalesced strips of sealing composition 17a and 17b, respectively. The strips of composition have increased film volume at their opposed end portions 17x and 17y, as shown in FIGURE 5.

In FIGURE 6, the body blank 20 of FIGURES 4 and 5 is shown after being formed into a substantially cylin drical shape prior to locking of the hooked side seam edges 21 and 23. After shaping, the strips of sealing composition are located on the interior surface of the can 'body along the marginal edges 22 and 24 which are subsequently outwardly'fian-ged for sealing engagement with a can lid. As shown, the strip of composition 17a extends around the circumference of the open can body along the inner surface of edge 22 with its opposed thickened end portions 17x and 17y positioned on the extremities 22a and 22b of edge 22 which are ultimately overlapped in the finished can body.

FIGURE 7 shows the flanged l-ap area generally designated 25 at one end of the completed can body of FIG URE 6. In the lap area 25, extremity 22b of edge 22 carrying a thickened end portion 17x of sealing strip 17a is superimposed on extremity 22a of edge 22 carrying the other thickened end portion 17y of sealing strip 17a. A can lid generally designated at is shown in position incident to double seaming to the flanged can body. An annular channel 31 of can end 30 carries a gasketing composition 32. The gasketing composition 32 in the channel 31 is not essential but may be used if desired. Ordinarily, the strip of sealing composition disposed around the inner circumferential edge of each of the can ends is sutficient to insure an effective hermetic seal with the end closures.

Sealing compositions which may effectively be applied to the sheet stock are composed of both a solid phase and a liquid phase, the latter of which may be aqueous or organic. The solid phase may contain any one of a variety of polymers having elastomeric properties; fillers; and resins. Suitable components include such polymers as butadiene-styrene copolymers, butadiene-styrene-acrylonitrile terpolymers and polychloroprene; such fillers as channel black, titanium dioxide, calcium carbonate, and zinc oxide; and such resins as esterified gum rosin, beta- -pinene, and zinc resinate. Other ingredients which may be incorporated into the composition, if desired, include antioxidants, processing aids, curing agents and so forth.

Representative sealing compositions which are particularly useful in the present invention are illustrated in Examples 1 to 4 below. All quantities given are in percent by weight unless specified otherwise.

Example 1 Example 2 A composition consisting of 8.73 weight percent of a low Mooney (20) -60 styrene-butadiene rubber, .09 percent of N,N di-beta-n-aphthyl-para-phenylenediamine, .02 percent channel black, .69 percent titanium dioxide, 3.93 percent talc, 23.04 percent calcium carbonate, 6.37 percent esterified gum rosin, 2.53 percent zinc resinate. .04 percent 0,0' dibenzamido diphenyl disulfide, and

54.59 percent of a paraffinic hydrocarbon 'boiling at F.

5 Example 3 A composition comprised of a butadiene-st yrene-acrylonitrile terpolymer dispersion containing rosin ester and filler and carried in a paraflinic hydrocarbon solvent.

Example 4 A com-position consisting of a butadiene-styrene rubber containing beta-pinene resin, filler and carried in a paraflinic hydrocarbon solvent.

I claim:

1. A can body blank having a strip of sealing composition disposed lengthwise on each of the opposed marginal edges which are ultimately interfolded with a can lid to form a double scam, the thickness of said strips being greatest at each of their opposed longitudinal end portions.

2. A tubular can body having opposed open ends and a side seam extending lengthwise from end to end, each of said open ends having a strip of sealing composition disposed around its inner circumferential edge, said strip at each open end being thicker at the junction with the side seam.

3. A tubular can having a side seam extending lengthwise from end to end and having at least one of its opposed ends intenfolded with a covering lid in double seamed relationship, each of said ends having a strip of sealing composition extending around its inner circumferential edge, said strip having opposed thickened end portions situated in the side seam.

4. A method of forming can body blanks which cornprises providing a length of can body-making material, disposing a sealing composition on said material in a plurality of spaced linear configurations of predetermined length, the disposition being such that a greater amount of composition is disposed at the longitudinal end portions of each linear configuration, and cutting the bodymaking material into individual body blanks so that each blank has a strip of sealing composition disposed lengthwise along each of the opposed marginal edges of the blank.

No references cited.

THERON E. CONDON, Primary Examiner.

J. B. MARBERT, Assistant Examiner. 

1. A CAN BODY BLANK HAVING A STRIP OF SEALING COMPOSITION DISPOSED LENGTHWISE ON EACH OF THE OPPOSED MARGINAL EDGES WHICH ARE ULTIMATELY INTERFOLDED WITH A CAN LID TO FORM A DOUBLE SEAM, THE THICKNESS OF SAID STRIPS BEING GREATEST AT EACH OF THEIR OPPOSED LONGITUDINAL END PORTIONS. 